Jazz and blues musicians often personify the very art of being cool, but we have to ponder whether they would be half as cool (musically speaking) if they didn’t constantly use 7ths in their music.

Altered chords are chords that have been changed by having the pitch of one or more notes in the chord sharpened or flattened by a semitone. Altering a chord in this way can have a big effect on its ...